bug fixed for issue #1474

src/main/java/com/alibaba/fastjson/serializer/JavaBeanSerializer.java

@@ -362,7 +362,29 @@ protected void write(JSONSerializer serializer, //
                     }
                 }
 
-                commaFlag = true;
+                boolean fieldUnwrappedNull = false;
+                if (fieldInfo.unwrapped
+                        && propertyValue instanceof Map) {
+                    Map map = ((Map) propertyValue);
+                    if (map.size() == 0) {
+                        fieldUnwrappedNull = true;
+                    } else if (!serializer.isEnabled(SerializerFeature.WriteMapNullValue)){
+                        boolean hasNotNull = false;
+                        for (Object value : map.values()) {
+                            if (value != null) {
+                                hasNotNull = true;
+                                break;
+                            }
+                        }
+                        if (!hasNotNull) {
+                            fieldUnwrappedNull = true;
+                        }
+                    }
+                }
+
+                if (!fieldUnwrappedNull) {
+                    commaFlag = true;
+                }
             }
 
             this.writeAfter(serializer, object, commaFlag ? ',' : '\0');

src/test/java/com/alibaba/json/bvt/issue_1400/Issue1474.java

@@ -0,0 +1,51 @@
+package com.alibaba.json.bvt.issue_1400;
+
+import com.alibaba.fastjson.JSON;
+import com.alibaba.fastjson.annotation.JSONField;
+import com.alibaba.fastjson.annotation.JSONType;
+import junit.framework.TestCase;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Issue1474 extends TestCase {
+    public void test_for_issue() throws Exception {
+        Map<String,Object> extraData = new HashMap<String,Object>();
+        extraData.put("ext_1", null);
+        extraData.put("ext_2", null);
+
+        People p = new People();
+        p.setId("001");
+        p.setName("顾客");
+        p.setExtraData(extraData);
+
+        assertEquals("{\"id\":\"001\",\"name\":\"顾客\"}", JSON.toJSONString(p));
+    }
+
+    @JSONType(asm = false)
+    static class People{
+        private String name;
+        private String id;
+        @JSONField(unwrapped=true)
+        private Object extraData;
+
+        public String getName() {
+            return name;
+        }
+        public void setName(String name) {
+            this.name = name;
+        }
+        public String getId() {
+            return id;
+        }
+        public void setId(String id) {
+            this.id = id;
+        }
+        public Object getExtraData() {
+            return extraData;
+        }
+        public void setExtraData(Object extraData) {
+            this.extraData = extraData;
+        }
+    }
+}